Can the shaky cease-fire announced this week avert a fresh disaster about to happen in Syria? The siege of Aleppo, Syria’s largest city. That will be the key test for the pact, which is to go into effect on Feb. 27. For weeks now, Aleppans have felt a sense of impending doom. Recently, Syrian government forces with the support of Russian air power cut off the last remaining major supply route to rebels in Aleppo, setting the stage for a siege. Fearing the prospect of bombardment and starvation, tens of thousands of Syrians have already fled toward Turkey and the hope of safety. With Ankara refusing to let most of them into the country, a humanitarian crisis is already brewing on the border. Many thousands more are fleeing to other parts of Syria, including to regime-held areas. A not-small percentage of them will end up on the road to Europe this spring and summer.

Ironically, the talks are not even any longer about bringing relief to Aleppo. It was the Assad regime’s advance on the city in early February that pushed international negotiations forward. But the talks are less likely to have any meaningful impact there than in other parts of Syria because fighting has dramatically intensified in and around Aleppo even as negotiations have progressed. And the Russians have made it clear that even if a cessation of hostilities comes into effect, Aleppo and the neighboring province of Idlib will be excluded from the arrangement due to the direct presence of Jabhat al-Nusra, Al Qaeda’s affiliate in Syria.

The fact that President Vladimir Putin came out so quickly in support of the agreement, making a special address on Russian television yesterday, at least holds out the prospect of a new commitment from Moscow. This is presumably based on the military gains Putin’s forces have helped Assad secure over recent months. And the Russian leader has reason to be confident he can control events on the ground: The presence of al-Nusra, in particular, gives Russia an excuse to keep fighting in Aleppo and even to target rebel fighters that the West would prefer to support. Washington knows it is impossible to craft a cease-fire that would still allow attacks on the Islamic State—which President Barack Obama wants—but rule out efforts against al-Nusra, which is a terrorist organization by any definition.

Many still see the ultimate answer in the use of U.S. military force or a no-fly or safe zone to save the people of Aleppo and to push back the Russian-supported regime advance. Such voices are demanding that Washington find a way to reopen supply routes into the city and increase the flow of high-end weapons to the rebels.

But just as constant in these refrains is the lack of a broader strategy in which to place the use of U.S. force. Beyond the fact that these measures would risk a direct U.S.-Russian clash and the possible outbreak of a wider conflict, it is doubtful whether safe zones would actually improve protection for civilians. Without an accompanying ground force able to secure the zones, fighting will continue. Al-Nusra and ISIL are likely to partly fill any vacuum. Pushing the regime back from northern Aleppo may change the identity of those who suffer, but it will hardly reduce the problem overall. Moreover, the regime and its Russian and Iranian allies will simply counterescalate. In the end, it is hard to understand a strategy that seeks to relieve the suffering of the Syrian people by sending in more weapons and creating more violence. We’ve seen this story of escalation and counterescalation many times before over the course of the Syrian war and it’s always had the same outcome: more misery for the local population.

There has to be a better way—and there is, even if there is no good way. The guiding principle must be to focus on efforts to help the people of Aleppo, not on achieving absolute political ends or a victory in the war, a sentiment that still animates far too many of the actors involved. It’s long past time to set aside the meaningless question of Bashar Assad’s future and to stop trying to micromanage a fictional Syrian transition. This may be succumbing to the strategy of Assad and the Russians, but civilian protection, humanitarian access and freezing the conflict before it reaches new heights of dangerous escalation must now be prioritized, nowhere more so than in Aleppo.

Instead it’s time to push the Syrian opposition to accept Russian cease-fire terms around Aleppo as the better long-term strategy. In the north of the country this means effectively pushing the opposition and its regional backers to accept that we cannot work with groups that cooperate with Nusra and that the presence of those groups in Aleppo will prevent any local cease-fire from taking hold. De-escalation on Russian terms is still better than no de-escalation at all.

It’s worth noting that demobilization is ultimately most threatening to Assad. The Syrian president has long known that he cannot survive longer-term political reform, and winning in Syria today is most likely to emerge as a result of a process of de-escalation that sees the regime exposed to the pressures of its own internal constituents and external backers, whatever the initial terms. So long as the Syrian struggle remains a military fight for regime survival both Russia and Iran will remain locked into Assad’s defense. But, as we saw again last week when Russia’s U.N. ambassador publically censored Assad for rejecting the cease-fire plan, the opening of an alternative space will expose him to pressure from his allies.

Talk of sending more arms or establishing safe zones will only encourage the opposition and prolong the war, initiating a new cycle of escalation. The U.S. government has long since concluded, accurately in our view, that it cannot win this war for the Syrian opposition. But it is the height of cruelty to give them just enough support and encouragement so as to not lose. Hope is the enemy of peace in Syria.

And bear in mind that time is running out. Aleppo is where any agreement is least likely to hold—and where any subsequent escalation of fighting risks collapsing the entire process, given the city’s wider symbolic and strategic prominence. The international community needs to build quickly on the cease-fire to pre-empt a looming humanitarian disaster in Aleppo. Otherwise, we will soon see suffering there beyond anything we have seen thus far in the Syrian civil war, even with its 300,000 dead.

Already the ongoing fight in Aleppo is predictably drawing in all the conflict’s key actors, determined to not leave the fate of the key city to others. On the opposition side, external backers are facilitating new weapon flows and Turkey is reportedly transporting fighters to the frontline via its own territory. Ankara has also begun shelling Kurdish forces seizing rebel-held towns in northern Aleppo under Russian air cover. ISIL is also moving in. The jihadist movement is positioned to the east of the city and as conditions deteriorate is looking to stake a wider claim. Aleppo in short contains all of the seeds for escalation and even a direct Russian-Turkish clash.

If the regime does succeed in laying siege to rebel areas of Aleppo, the result will almost certainly be an uncontrolled humanitarian disaster. Rebel-held eastern Aleppo is still home to an estimated 350,000 people, many times the size of previous sieges in Homs or Madaya. Moreover, the Russian air force is now fully on the scene, bringing with it a counterinsurgency strategy formed on the mean streets of Grozny, the capital of Russia’s rebellious Chechen province. That strategy holds that insurgents cannot hide among the people of a city if there is no city and there are no people. And it will also be worse because rebels are less likely to be willing to surrender in so strategic a location, in part because there are a dwindling number of other rebel-held areas they could head to as part of any surrender package.

All of this means that sustainable progress elsewhere is almost certainly going to need progress around Aleppo. A further deterioration of the situation here would almost certainly suck out all the air of the wider agreement. The urgent priority must now be to think about how to translate gains to this key city.

This approach must simultaneously be accompanied by a greater focus on the deteriorating Kurdish–Turkish relationship. There is no prospect of a freeze in the wider conflict around Aleppo, especially if largely on Russian terms, without Turkish buy-in and the U.S. needs to step up its pressure on Kurds to halt their advances eastward and the seizure of rebel-held villages.

If all of this fails and there is no hope of progress in the north, a bit of deterrence against the Russians is in order—just not through force, which will only be self-defeating. Measures aimed at the Russians should take advantage of more sanctions, an instrument the West would actually use and the Russians actually fear. The United States and Europe should pre-announce further sanctions, particularly financial sanctions, against Russians if humanitarian access is not maintained in Aleppo. Even as we challenge the Russians, we need to recognize that ultimately, and however much we dislike it, the road toward averting a humanitarian disaster in Aleppo runs through Moscow.